1. Field of the Invention
The invention relates to a method of recording digital information signals on a removable rewritable disc like recording medium, the method comprising submitting fixed sized packets of user information for recording on the disc, the packets having a minimum packet size, allocating said packets to continuous sectors on the disc in a data area, said sectors having a minimum addressable sector size smaller than the minimum packet size, wherein said allocating comprises reallocating defect areas to a spare area on the disc, and recording said packets on the disc along a spiral track.
The invention further relates to an apparatus for recording/reproducing digital information signals on/from a removable rewritable disc like recording medium, the apparatus comprising input means for receiving signals representing fixed sized packets of user information for recording on the disc, the packets having a minimum packet size, allocating means for allocating said packets to continuous sectors on the disc in a data area, said sectors having a minimum addressable sector size smaller than the minimum packet size, defect management means for reallocating defect areas to a spare area on the disc, and recording means for recording the signals representing user data along a spiral track on the disc.
2. Description of the Related Art
The PC world needs a replacement for the floppy drive. A rewritable storage medium of the disc-like optical type, such as the CD-RW, seems to be a logical choice because the read function of the magnetic floppy is already replaced by the CD-ROM. All PC's today are equipped with a CD-ROM and applications and software are distributed on CD-ROM. Therefore, a recording medium like CD-RW or rewritable DVD, seems to be the perfect media to fill in the needed write capability. MO and ZIP/Jazz already tried to fill this gap, but they all miss compatibility with the installed base. That is exactly what CD-RW, for instance, can deliver with the installed base of over approximately 200 million CD-ROM drives (MR1.0 compatible). RW media are cheap and the capacity is sufficient for floppy use.
Furthermore, manufacturers of operating systems want to get rid of legacy material like the floppy drive. For OEM companies, the idea is attractive, as they can replace the floppy drive, the CD-ROM and the DVD-ROM drive by a one spindle drive, like a Combi, and by a double writer in the future. It will also add a new feature to the drive other than the ever increasing speed.
There are products on the market (like DirectCD) which enable using a CD-RW like a floppy drive, but they don't behave the way one would expect a CD floppy drive to behave. The access time is too low, formatting time is too long and, more important, the drive does not fit into the strategy of current OS. The disc should be immediately available for dragging and dropping of files. A fast eject is required, deleting should be instant. Due to enable multiple drag and drop, a defect management is required. However, the defect management should be done by the drive. This opens the way to use UDF 1.02 instead of UDF1.5, which will not be supported on the write side by Microsoft. Further background formatting must be done by the drive and not by the application or OS to minimize bus traffic, and interaction between the drive and the OS. Finally, Read/Modify/Write for packets should be done by the drive.
Such a method and apparatus is disclosed in European Patent Application No. EP 99203111.2, corresponding to U.S. Pat. Nos. 6,606,285 and 6,760,288, and European Patent Application No. EP 00200290.5, both incorporated by reference.
However, the method of defect management disclosed is limited to one-packet based replacements, the size of the replacement packets being the same as the size of the write-packet. For instance, in case of CD-RW, both sizes are 64 kB or 32 sectors. Although this is sufficient to cover Disk-Over-Write (DOW) problems of RW media, it appears to be inefficient with respect to robustness for local physical defects, like finger prints, scratches and media weak-spots. DOW tends to wear out sectors equally within one written packets. Thus, it makes a lot of sense to replace the whole unity in one step, since the indication that a part (2 kB-sector) of the packet is wearing out can be interpreted as a wear-out warning for the whole packet. But due to the spiral-groove structure of an optical record carrier, non-DOW defects, like the ones mentioned above, will typically appear on neighborhood tracks. For example, a scratch of 3.5 cm from inner to outer diameter across the disk affects approximately 3.5 cm/1.5 μm=23300 tracks, in case of an CD-RW disk. This implies approximately 21000*64 kByte=1344 Mbyte. With a 74 min CD-RW disc with 500 Mbyte user area and approximately 40 Mb spare area, this is clearly not feasible.